Restructure documentation. Now the documentation has installation, administration, usage, development, contributing the 5 main parts (#23629)

- **Installation**: includes how to install Gitea and related other
tools, also includes upgrade Gitea
- **Administration**: includes how to configure Gitea, customize Gitea
and manage Gitea instance out of Gitea admin UI
- **Usage**: includes how to use Gitea's functionalities. A sub
documentation is about packages, in future we could also include CI/CD
and others.
- **Development**: includes how to integrate with Gitea's API, how to
develop new features within Gitea
- **Contributing**: includes how to contribute code to Gitea
repositories.

After this is merged, I think we can have a sub-documentation of `Usage`
part named `Actions` to describe how to use Gitea actions

---------

Co-authored-by: John Olheiser <john.olheiser@gmail.com>

docs/content/doc/developers/integrations.zh-tw.md

@@ -1,22 +0,0 @@
----
-date: "2019-04-15T17:29:00+08:00"
-title: "整合"
-slug: "integrations"
-weight: 40
-toc: false
-draft: false
-menu:
-  sidebar:
-    parent: "developers"
-    name: "整合"
-    weight: 65
-    identifier: "integrations"
----
-
-# 整合
-
-Gitea 有著很棒的第三方整合社群， 以及其它有著一流支援的專案。
-
-我們持續的整理一份清單以追蹤他們！請到 [awesome-gitea](https://gitea.com/gitea/awesome-gitea) 查看。
-
-如果您正在找尋有關 [CI/CD](https://gitea.com/gitea/awesome-gitea#user-content-devops)、[SDK](https://gitea.com/gitea/awesome-gitea#user-content-sdk) 或是其它佈景主題，您可以在存儲庫 [awesome-gitea](https://gitea.com/gitea/awesome-gitea) 找到他們。